1. Field of the Invention
The present invention relates to a method of particle-dispersed liquid, and more particularly to a method of separating and removing larger particles and/or indeterminately shaped particles in a particle-dispersed liquid by using micro-flow passages. The invention further relates to an apparatus for producing particle-dispersed liquid, having micro-flow passages.
2. Description of the Related Art
The particle classification methods include a dry method and a wet method.
The dry methods include a high accuracy method since a difference between the specific gravity of a fluid and that of particles becomes large.
In the wet method, a difference between the specific gravity of a liquid and that of particles becomes small but particles are dispersed easily in a liquid, so that a high classification accuracy is obtained with respect to, especially, a powder region. Both the dry method and wet method having generally a rotating portion and adapted to classify particles on the basis of the balance of the centrifugal force and inertial force constitute the main methods. However, due to the provision of the rotating portion, there are problems of contamination of the apparatus due to the abrasion of the part and problems of the cleaning of the apparatus. In the dry method, a classifier not having a rotating portion and utilizing the “Coanda effect” has been commoditized but, in the wet method, an efficient classifier not having a rotating portion has not yet been obtained.
The methods of removing larger particles contained in particles include a method of removing the same by using a filter and the like having uniform pores. However, even in a batch type filter, the clogging thereof with contaminants and the like occurs. Therefore, such a filter has a low operational efficiency, and causes an increase in the diameter of the pores during a long use thereof, so that the accuracy lowers.
In the meantime, various kinds of methods and apparatuses for conducting a chemical reaction, a unit operation and the like in micro-regions have been studied in recent years, and methods and apparatuses for classifying particles efficiently without causing the contamination of the apparatus to occur have been discussed.
An Non-Patent Document 1 proposes a method of enabling the classification of particles in the direction perpendicular to the flows thereof to be done as the method of and the apparatus for classifying particles by only introducing particles, by using micro-channels (pinched channels) having partially narrowed portions and utilizing profiles of the characteristic flows in the micro-channels. In this method, it has been reported the separation of particles of 15 μm and particles of 30 μm from each other can be carried out.
In a Non-Patent Document 2, a method of separating and classifying particles by micro-channels having arcuate rectangular cross-sections is reported.
In the former method/apparatus, it is necessary that the width of a laminar flow be reduced to not larger than the particle size, and the method/apparatus has many problems in practical use thereof. In the latter method, an eddy current occurs, and particles of which the diameters are small are mixed in the flow in the outermost flow passage, so that the separation of particles (larger-diameter particles) only having larger particle sizes cannot be carried out.
Although it is also demanded that the separation of particles of higher degree of indeterminate shapes be made, there is not a method which has been put into practical use for this purpose.
The Patent Document 1 discloses an apparatus for mixing or separating a fluid capable of preventing reaction products from being deposited on a flow channel wall, and capable of being produced with a high efficiency. However, this apparatus/system, a method of separating larger-diameter particles only contained in a micron-order particle-dispersed liquid is not referred to. Especially, a method of efficiently separating indeterminately shaped particles only is not described either.
[Patent Document 1] US2004/0213083 A1
[Non-Patent Document 1] 69th-year Collection of Manuscripts of the Academic Circle of the Chemical Engineering, No. 201 “Development of a Method of Continuously Classifying Fine Particles Using Micro-Channel Layer Flow System” (Seki et al)
[Non-Patent Document 2] 69th-year Collection of Manuscripts of the Academic Circle of the Chemical Engineering, No. 202 “Discussion of Behavior in a Micro-Separation Classification Apparatus by Euler-Lagrange Method” (Ogawara et al)